1. Field of the Invention
In general, the present invention relates to motor vehicles that are powered by fuel cells. More particularly, the present invention relates to systems used to supply hydrogen gas to the fuel cell during the operation of the motor vehicle.
2. Prior Art Description
Due to the concerns of green house gas emissions and fuel costs, automobile manufacturers have been attempting to create automobiles that run on alternate fuel sources. For example, some city buses have been manufactured that burn hydrogen gas instead of gasoline. When hydrogen gas burns, it creates only water, thereby eliminating pollution from the bus engines.
One of the largest problems associated with vehicles that burn hydrogen gas is how to refuel those vehicles. Hydrogen has must be kept in storage tanks at relatively high pressures. Accordingly, in order to support a vehicle that burns hydrogen, large volumes of hydrogen must be produced at an industrial source. The hydrogen gas must then be trucked to a refill station in specialized tanker trucks. Once at the refill station, the hydrogen gas must be transferred under pressure to the storage tanks at the refill station. The refill station then holds the hydrogen until needed by the vehicles. Hydrogen gas is highly reactive. Accordingly, all transportation tanks, storage tanks and transfer pipelines must be made of high strength, non-reactive materials, such as stainless steel.
The infrastructure needed to supply hydrogen is complex and costly. If even a small percentage of vehicles ran on hydrogen, the U.S. industrial capacity to produce hydrogen would soon be exhausted. Furthermore, there would not be enough pressurized tanker trucks and freight cars available to distribute the required hydrogen. It is primarily due to these supply infrastructure problems that hydrogen fueled vehicles have been limited to specialized applications, such as city buses, where the expense of the system is subsidized by the government.
Electric vehicles are yet another approach to reducing pollution and fuel consumption by vehicles. Some electric automobiles are powered solely by rechargeable batteries. The rechargeable batteries are recharged from an external power source when the automobile is not in use. Such electric cars have many disadvantages that limit their appeal to the general public. For example, such electric cars require large expensive batteries that contain highly toxic materials. Furthermore, such electric cars must be plugged into an external power source and recharged. Accordingly, the vehicle is not always available for use.
In an attempt to make electric automobiles more practical, hybrid vehicles have been created. Hybrid vehicles contain an internal combustion engine that both powers the vehicle and recharges rechargeable batteries. During certain driving situations, the hybrid vehicle powers itself using electricity stored in the batteries.
Although hybrid vehicles have better gas mileage than do traditional gasoline engine vehicles, hybrid vehicle still burn hydrocarbon fuel inefficiently. Accordingly, such vehicles still add significantly to air pollution and global warming.
It has long been desired to produce a vehicle that runs on electricity yet does not require recharging or a back-up internal combustion engine. One of the most practical ways to fulfill this need is to power the vehicle with a proton exchange membrane (PEM) fuel cell. A PEM fuel cell creates electricity from hydrogen gas. The electricity is used to run electric motors that drive the wheels of the vehicle. A PEM fuel cell creates no greenhouse gases. However, a PEM fuel cell requires the use of ultrapure hydrogen gas. Ultrapure hydrogen gas is hydrogen gas that is at least 99.999% pure. If such pure hydrogen gas is not used, the PEM fuel cell will quickly fail. It will therefore be understood that if a vehicle runs on a PEM fuel cell, that vehicle has the same refueling problems as does a vehicle that burns hydrogen, plus the added complication that the hydrogen must be ultrapure. Accordingly, until now, vehicles that have PEM fuel cells have been more expensive and less practical than even vehicles that burn hydrogen.
In order for a vehicle with a PEM fuel cell to become practical, a need exists for providing ultrapure hydrogen to the vehicle in a cost efficient manner. This need is met by the present invention as described and claimed below.